1. Field of the Invention
The present invention is directed to a system that analyzes and characterizes the bandwidth of an input signal and, more particularly, to a system which will measure the bandwidth of input signals and locate and quantify holes and/or drop outs within that bandwidth in a high noise environment.
2. Description of the Related Art
Bandwidth measurements have been performed for many years in the fields of radar and communication system testing. Various techniques have been developed to automate the measurement of signal bandwidths utilizing a spectrum analyzer or scaler network analyzer to obtain a digitized representation of the signal bandwidth. Several systems have been developed to allow a computer to process the digitized data and determine the signal bandwidth. These algorithms vary in complexity from a simple "three dB down from maximum" technique to complex special case techniques. The simple solutions are rarely adequate because they require a very flat, noise free sample where the edges are well defined, while the special case solutions are rarely adequate to handle the wide range of requirements imposed by general purpose testing. The Hewlett Packard HP 8566B spectrum analyzer includes a bandwidth measurement algorithm which requires a relatively clean signal. This system will not accurately measure the bandwidth in the presence of holes or drop outs in the signal spectrum. U.S. Pat. No. 4,794,324 is directed to a technique that allows a computer to control a spectrum analyzer over an IEEE-STD-488 bus to make bandwidth measurements. The technique of the U.S. Pat. No. 4,794,324 was developed to measure noise type signals utilizing the maximum hold feature of the spectrum analyzer. However, the technique described in the U.S. Pat. No. 4,794,324 requires multiple samples, works for bandpass signals only, does not work in the presence of holes or drop outs in the spectrum and does not work for multiple bandwidths. As a result of the deficiencies in the prior art spectrum analyzers, the test personnel would resort to manual examination of the spectrum analyzer screen, so that quite often the speed, validity and repeatability of the manual test results depends upon the skill and thoroughness of the operator. Since the presence of a signal spectrum with holes and/or drop outs is becoming more and more prevalent in the state of art communications and radar equipment now being tested and, in the face of growing concern over test speed and validity, a method of automatic bandwidth analysis which will handle high noise environments with holes and/or drop outs is needed.